1. Field of the Invention
The present invention relates generally to wafer rinsing apparatuses, and more particularly, wafer rinsing apparatuses with improved rinsing effects.
2. Description of the Background Art
Manufacturing processes of super large scale integrated circuit devices of the time demand a more efficient technique of rinsing wafer surface in order to improve a yield and quality of the devices. Contaminants such as resist residues, fine particles, organic films and native oxide films are among principal factors which determine a yield and performance of devices. For submicron devices, contaminated particles on the order of 0.1 .mu.m should be removed.
FIG. 5 is a schematic diagram showing a conventional wafer rinsing apparatus for rinsing a wafer by jetting ice particles on the wafer.
The conventional wafer rinsing apparatus includes an ice making hopper 1 for making ice particles by heat exchange between fine droplets of liquid to be frozen and low-temperature liquefied gas. Ice making hopper 1 is provided with a supply spray 2 for supplying fine droplets of liquid to be frozen to ice making hopper 1. The liquid to be frozen with particles removed by a filter 3 is fed to supply spray 2. Ice making hopper 1 is provided with a supply spray 4 of low-temperature liquefied gas (hereinafter simply referred to as liquefied gas). The liquefied gas is fed to supply spray 4 through a filter 5. Supply spray 4 and filter 5 are connected by a piping 20. Ice making hopper 1 is coupled to a spray means 9. Jet nozzle 9 is arranged in a washing vessel 7. A wafer 6 is disposed in washing vessel 7. With reference to FIGS. 5 and 6, wafer 6 is held and rotated by a roller 8. Provided in washing vessel 7 is a pure water nozzle 10 for spraying pure water onto the surface of wafer 6.
Operation of the conventional wafer rinsing apparatus will be described. Particles included in liquefied gas such as liquid nitrogen are removed by filter 5. The liquefied gas with particles removed is fed to ice making hopper 1 by supply spray 4, thereby cooling ice making hopper 1 to about -100.degree. C.--150.degree. C. Then, particles included in liquid to be frozen such as pure water are removed by filter 3 and the pure water with the particles removed is supplied to the ice making hopper by supply spray 2. The supply of the liquefied gas and that of the liquid to be frozen to ice making hopper 1 are carried out substantially at the same time. The fine droplets of the liquid to be frozen are made into ice particles 30 by heat exchange with the liquefied gas. The liquefied gas supply sprays 4 are provided in plural in order to efficiently execute the heat exchange. The liquefied gas is sprayed into ice making hopper 1 and vaporized therein. Heat of the vaporization is used to make the fine droplets of liquid to be frozen into ice particles 30. The diameter of the obtained ice particles is several .mu.m-50 .mu.m. Ice making hopper 1 is made of SUS materials and filter 3 is made of SUS materials or ceramic materials. Ice particles 30 formed in ice making hopper 1 are drawn by jet nozzle 9 disposed in washing vessel 7 and sprayed onto wafer 6. Jet nozzle 9 is formed by an ejector using dry air or nitrogen gas as a carrier gas.
Wafer 6 is held by roller 8 provided in washing vessel 7. When the ice particles 30 are jetted, wafer 6 is moved up-and-down and rightward and leftward and rotated by roller 8, so that the ice particles 30 are jetted onto the entire surface of wafer 6. In addition, pure water is sprayed onto wafer 6 from pure water nozzle 10 in order to enhance a rinsing effect when the ice particles 30 are jetted.
With the conventional wafer rinsing apparatus thus structured as shown in FIG. 5, dusts are formed at piping 20, ice making hopper 1, supply spray 4 and filter 5 which contact with the liquefied gas, whereby particles such as Fe, Ni and Cr having a diameter smaller than that of the ice particles are formed. The particles, together with the ice particles 30, are jetted onto wafer 6 to contaminate and damage the same.
The mechanism of dust formation is as follows. When liquid nitrogen contacts an inner wall surface of an ice making hopper made of the SUS materials, for example, the liquid nitrogen is vaporized on the inner wall surface of the ice making hopper to suddenly expand the hopper. Such sudden expansion peels off particles of such as Fe, Ni and Cr from the SUS materials to form dusts.